1. Field of the Invention
The present invention concerns an electric terminal for attachment to a contact bar or carrying rail which has a U-shaped cross-section with outwardly projecting flanges at the coplanar ends of the shanks of the U which terminal has a retaining foot with claws directed towards each other for engaging the two flanges of the contact bar, wherein a recess is provided between each claw and the retaining foot for accommodating one of the flanges of the contact bar.
2. Description of the Prior Art
Contact bars or carrying rails of this type are frequently used for mounting electrical terminal blocks and wiring apparatus and expediently have standardised cross-sectional dimensions according to (German standard) DIN 46277, Sheet 2, 3 or 4 or according to European Standard EN 50022.
Electrical terminals of the above-mentioned characteristics are shown for instance in Swiss patent specification No. 531,266; according to FIGS. 2, 3 and 6 of this specification the claws are formed on resiliently bendable limbs and are so constructed that on pressing the terminal against the flanges of the contact bar, they automatically spring back and finally under the resilient effect of the limbs, snap automatically under the flanges. Also, this terminal may without further measures be pulled off the contact bar by overcoming the retaining force exerted by the resilient limbs and claws on the flanges. Furthermore, a terminal of the above-mentioned type is known, e.g. from West German patent specification No. 2,051,781 wherein one of the two mutually oppositely lying claws is constructed to be rigid whilst the other is resiliently yieldable and is made from spring wire or leaf spring material. In both of these mentioned cases the retention of the terminal on the contact bar is sufficient mechanically to fix the terminal but is insufficient to provide a completely objection-free electrically conductive coupling between the contact bar and the retaining foot of the terminal, such as is required e.g. for protective earthing (grounding).
However, from Swiss patent specification No. 532,253 a terminal of the above-mentioned kind is known wherein the two mutually oppositely lying claws are constructed rigidly and one of these claws is associated with an adjusting screw, which enables the relevant flange of the contact bar to be rigidly clamped between the said claw and one of the ends of the adjusting screw in order mechanically to fix the terminal on the contact bar and simultaneously to ensure good electrical connection between the contact bar and the terminal, insofar as the retaining foot and the claws as well as the contact bar are made of metal. In this way, a terminal of the last-described kind may also be used, e.g. as a protective conductor terminal. A certain disadvantage may be seen in that the other claw, not being associated with an adjusting screw of its own, is not clamped rigidly to the same extent to the contact bar. To remove this disadvantage a second adjusting screw would be necessary.